I-84 bridge work poses flooding risk

Springfield-based Hamilton Construction in June began work to replace the Interstate 84 bridge over the Sandy River near Troutdale. Construction work could exacerbate any flooding during the project, so Hamilton has taken steps to mitigate flood risk, and ODOT has offered to pay flood insurance premiums for homeowners nearby. (Photo by Dan Carter/DJC)

When work began in June on the Interstate 84 bridge replacement project over the Sandy River, the construction team was prepared for the in-water work window and other common challenges. But it was blindsided by another: flood risk.

When setting the first hundred of the project’s roughly 400 pilings, the general contractor, Hamilton Construction, realized that if a flood were to occur during the project, the amount of equipment and material the company had in the water could exacerbate the disaster.

So the contractor teamed up with the Oregon Department of Transportation, the project owner, to reorganize how the work is handled. Also, ODOT will cover homeowners’ flood insurance premiums during the project.

“The bridge has been standing for over 50 years, so no one had any idea of the effect the project would have on the river in the case of a flood,” said Brad Wurfel, spokesperson for ODOT. “Every part of a river is different, so the exact impact of the project couldn’t be assessed until hydrology studies were complete and work began.”

The area is already susceptible to flooding because the bridge spans a delta in the Sandy River and is near the Columbia River. When both rivers back up, water is pushed to the delta and levels rise.

High water levels and rain caused flooding in 1996, when numerous riverside properties around Troutdale were damaged and one person died.

“The people who live on the river have not forgotten what happened in 1996,” said Jack Glass, who has lived along the river for 27 years and owns a company called Team Hook Up Guide Service.

Because of the resonating effects of the 1996 flood, ODOT thought it best to cover the flood insurance premiums of any insured homeowner who lives within the predicted 100-year flood zone. ODOT has estimated there is a 2.7 percent chance that such a flood could take place during the construction time frame, which runs through 2013. Major flooding occurred in Troutdale in 1947, 1964 and 1996.

“Safety is our number one priority, but it’s usually focused around keeping our workers safe,” Wurfel said. “After realizing that the project had a potential impact on surrounding residents, and noticing how fresh the 1996 flood was in the minds of residents, we knew we had to do something.”

Nearly 60 properties are located within the zone. ODOT has set aside $500,000 to cover the insurance premiums over the next three years. But that number may have to be reevaluated if the project timeline is extended.

“It always seems like (the state is) taking things away from us, but in this case, (it’s) giving back,” Glass said.

The amount of material and equipment in the river for an Interstate 84 bridge replacement project causes water levels to rise. Hamilton Construction will remove the temporary work bridge during winter months to reduce the risk of flooding. (Photo by Dan Carter/DJC)

Federal regulations require anyone with a mortgage on usable property within 32 feet of a riverbank to obtain flood insurance. However, people who own their property outright are not subject to that requirement.

“Hopefully this will encourage people who don’t have flood insurance to get it,” Wurfel said.

But insurance won’t mitigate any project impacts that could increase flood risk, Wurfel said. So Hamilton Construction will remove one of the three temporary structures from the river in order to lower water levels in wintertime.

“It’s definitely going to cost money and time,” said Wendell Snook, a project manager with Hamilton. “But compared to the damages a flood could cause, the costs are really miniscule.”

There are 20 spans of work bridge – the temporary bridge that will be removed – and the cost of removal and reinstallation is between $5,000 and $10,000, Snook said. The final cost won’t be identified until the company knows how many spans will be removed.

The company will be running a yarder – much like the type used in the logging industry – to keep debris out of the water. The yarder could further contribute to flood risk.

Also, Hamilton and ODOT will approach various regulatory officials about possibly extending the in-water work window, which currently is from July 15 to Aug. 30. The window is set so that projects don’t interfere with salmon runs in the river.

“It’s going to be very difficult to maintain the schedule of a fall 2013 completion, especially if the window isn’t extended,” Snook said. “Getting the work fit into that short time frame was the biggest concern of this project until the flood issues were brought up a few weeks ago.”

The $73.6 million project is the last and biggest included in ODOT’s bundle of Interstate 84 bridge replacement projects. Funding for the $133.2 million worth of work, which involves replacing 21 spans along the interstate, came out of the third installment of the Oregon Transportation Investment Act, a $2.46 billion package approved by state legislators in 2003.